markdownlint/doc-build/md022.md

This rule is triggered when headings (any style) are either not preceded or not
followed by at least one blank line:

```markdown
# Heading 1
Some text

Some more text
## Heading 2
```

To fix this, ensure that all headings have a blank line both before and after
(except where the heading is at the beginning or end of the document):

```markdown
# Heading 1

Some text

Some more text

## Heading 2
```

The `lines_above` and `lines_below` parameters can be used to specify a
different number of blank lines (including `0`) above or below each heading.
If the value `-1` is used for either parameter, any number of blank lines is
allowed. To customize the number of lines above or below each heading level
individually, specify a `number[]` where values correspond to heading levels
1-6 (in order).

Notes: If `lines_above` or `lines_below` are configured to require more than one
blank line, [MD012/no-multiple-blanks](md012.md) should also be customized. This
rule checks for *at least* as many blank lines as specified; any extra blank
lines are ignored.

Rationale: Aside from aesthetic reasons, some parsers, including `kramdown`,
will not parse headings that don't have a blank line before, and will parse them
as regular text.